A choral instructional system is illustrated in U.S. Pat. No. 2,123,258 wherein it is provided for two interconnected turntables to play specially produced records, each containing two parts of a four-part harmony. Each of said records is used to feed audio to two sections of a choir with low pass and high pass filters employed to increase the loudness of the appropriate harmonic part, with such filtered outputs feeding the entire pertaining section of the choir.
The aforementioned system did not allow the repetition of a particular portion of the music selection without listening to the entire selection from the beginning, nor did it allow the listener individual control of the volume or select the individual part he desires to hear. Furthermore, a monitoring of all harmonic parts together required the playing of another record separately.
U.S. Pat. No. 2,844,663 discloses the use of a number of loud speakers positionable at selected locations to simulate the arrangement of a group of musical instruments for performance before an audience. Only the main operator selects the tracks to be played and the volume at which each speaker operates.
Accordingly, it is an important object of the present invention to provide an audio teaching system for use in choral instruction wherein a four-channel cassette recorder/player is utilized in conjunction with specially prepared tapes having the four harmonic parts, soprano, alto, tenor and bass, recorded on separate channels, whereby the choir practices the music selection with each member monitoring the appropriate harmonic part via an earphone.
Another important object of the invention is to provide full syncronization of the four harmonic parts so that any portion of the music selection may be repeated at random.
Another important object of the invention is to provide individual control boxes whereby each listener selects a volume level and one or all of the harmonic parts.
Still another important object of the invention is to provide components with compact dimensions so as to make the system fully portable.
Another important object of the invention is the provision of a choral instructional system wherein a plurality of controlled boxes are connected in series, each box being for a participant and including an amplifier having volume control wherein each participant may control the volume at which that participant desires to hear a selected part. A single earphone is provided at each station or control box so that a participant may hear a selected part at a selected level of sound while leaving one ear free to hear the sounds around them in a closed system without interference with a neighbor.
This system is designed to accommodate any number of individual control boxes from one to one hundred twenty without loss of signal level or degradation of audio signal quality to any individual control box.
Another important object of the invention is the provision of means for connecting and disconnecting and positioning the control boxes at each station whereby a control box may be connected or disconnected and replaced when a given control box is out of operation and wherein a cord is provided of selectable length coming from the control box. Means are also provided for positioning the respective control boxes for convenient use by each participant. This interconnecting system allows for efficient change in choir formation and position to accommodate varying needs of choral groups.